It's a statue/decorative bust for a dungeon entrance, so as he's highlighted it's meant to be like that
. I imagine the final will have cracks and chips out of it and look alot more stone or possibly metal.
For the anger of the face, the eyebrows seem to be curving the wrong way. In the concept the brows form a kind of "tick" shape coming round from the middle to an apex just above the eye and then curve upwards until they disapear, yours seem to curve downwards if you get what i mean, even though they're going upwards, the curvature is pathing down.
The nose area also needs to be pushed up a bit, in the concept it gives the effect of a scrunched nose which people and animals get when they snarl or shout which adds to the angry expression.
Looking good so far though